Preparation Method and Magnetic Properties of Large-Size Bulk (Nd, Dy)FeB Magnets Obtained via Dy Diffusion Treatment During Sintering Process

Grain boundary diffusion in Dy vapor was conducted during sintering to prepare large-sized bulk (Nd, Dy)FeB magnets. The morphologies, elemental compositions, and magnetic properties of the (Nd, Dy)FeB magnets were analyzed via scanning electron microscopy, energy spectrum analysis, X-ray diffraction, plasma emission spectrometry, and magnetic property testing. The effects of diffusion sequence, temperature, and time on the Dy distribution and magnetic properties were systematically investigated. The effective penetration depth of Dy exceeded 15 mm in the bulk (Nd, Dy)FeB magnets obtained via the grain boundary diffusion method. The optimized ΔHcj/ΔBr was up to 23.08 in the bulk (Nd, Dy)FeB magnets obtained under diffusion temperature of 980 °C and diffusion time of 8 h, which is much higher than that of the magnets obtained via Dy powder doping.